Code
   <script type="text/javascript">
    window.onload = function() 
    {
        if (document.getElementsByTagName)
        {
            var s = document.getElementsByTagName("select");
            if (s.length > 0)
            {
                window.select_current = new Array();
                for (var i=0, select; select = s[i]; i++)
                {
                    select.onfocus = function()
                    {
                        window.select_current[this.id] = this.selectedIndex;
                    }
                    select.onchange = function()
                    {
                        restore(this);
                    }
                    emulate(select);
                }
            }
        }
    }

    function restore(e)
    {
        if (e.options[e.selectedIndex].disabled)
        {
            e.selectedIndex = window.select_current[e.id];
        }
    }

    function emulate(e)
    {
        for (var i=0, option; option = e.options[i]; i++)
        {
            if (option.disabled)
            {
                option.style.color = "graytext";
            }else{
                option.style.color = "menutext";
            }
        }
    } 
    </script>